Aiming at the problem that due to randomness, intermittency and periodicity of photovoltaic power generation, a confidence capacity of power generation of a large-scale photovoltaic power station group in China cannot be accurately evaluated, the present invention discloses a photovoltaic power station group confidence capacity evaluation method. The photovoltaic power station group confidence capacity evaluation method is characterized by comprising the steps of power characteristic analysis of a photovoltaic power station group, power modeling of the photovoltaic power station group, which considers power correlation, photovoltaic power generation confidence capacity evaluation and the like. According to the photovoltaic power station group confidence capacity evaluation method, a power correlation coefficient is used for representing power correlation of different photovoltaic power stations in the same photovoltaic power station group; a power model for the photovoltaic power station group, which considers the temperature, irradiance variation and power correlation, is constructed; by the model, the power of the photovoltaic power stations is simulated and the confidence capacity of the photovoltaic power station group is evaluated; and the photovoltaic power station group confidence capacity evaluation method has the characteristics of scientificity, reasonability and high applicability.